I think I posted this in another thread. I cleaned up the gas cap and the filler cap insert and got rid of some grime, I let the system run a couple of cycles and the code reset itself and hasn't come back.

I've seen them leak at the fuel sender unit o-ring on the tank. Try the little (easy) fixes first, or take it into a shop that has a smoke machine, they hook up the smoke machine and pump smoke through the evap system and look where the smoke is coming out from.